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The world-class Mehdiabad nonsulfide deposit consists of several accumulations of Zn–Pb–Fe nonsulfide minerals, derived from supergene of a vent-proximal sub-seafloor replacement SEDEX-type deposit hosted in lower Cretaceous clastic–carbonate rocks of the Taft and Abkuh Formations. The main sulfides are galena, sphalerite, pyrite, and minor amounts of chalcopyrite, which have been partially or completely transformed into nonsulfide minerals by supergene processes. Currently, the Zn mineralization in the Abkuh Formation (ore horizon II) is almost fully oxidized: the Mehdiabad deposit which can be assigned to both direct replacement and wall-rock replacement types. The time of the formation of the nonsulfide deposit has not been determined, but it is probable that the main supergene metallogenesis happened during Tertiary, possibly between post-Cretaceous to present. The mineralogy of the nonsulfide mineralization is generally complex and consists of smithsonite, hydrozincite, and hemimorphite as the main economic minerals, accompanied by cerussite, anglesite, iron–manganese oxy-hydroxides, sauconite, and Zn-rich clays. Commonly, nonsulfide minerals in this deposit consist of two types of ore: red zinc ore (RZO), rich in Zn, Fe, Pb-(As), and white zinc ore (WZO), typically with very high zinc grades but low concentrations of iron and lead. The proposed three-step scenario for the deposition of nonsulfide mineralization in the Mehdiabad deposit comprises: (1) the deposition of primary sulfides contemporaneous with lower Cretaceous clastic–carbonate host rocks to form SEDEX-type mineralization; (2) during the Late Cretaceous to present, regional uplift leads to deformation, folding, and thrusting of sulfide-bearing lower Cretaceous sequence; and (3) as a result, Zn–Pb–Fe sulfides hosted in carbonates experienced oxidation under an arid-warm climate to form the supergene nonsulfide ore mineralizations.

Shaimerden oxidized zinc ore containing more than 21% wt.% zinc is studied in this work. When the first research on hydrometallurgical processing of this ore was conducted the authors of this research determined the following parameters for ore leaching: the size of ore reduction, sulfuric acid concentration, temperature, and leaching duration. These tests serve as a basis for zinc recovery from the given ore with a size of – 2.5 mm and a regime is recommended providing zinc recovery into solution at the level 93.5%. However, the production regime proposed for sulfuric-acid leaching of this zinc ore requires further development as this process is characterized by inadequate production, high energy consumption for heating leaching pulp, and considerable sulfuric acid consumption. In order to avoid these disadvantages the authors develop a production regime of four-stage sulfuric-acid leaching of Shaimerden ore – 1.0 mm in size. The regime developed in this article provides zinc recovery from ore into solution at the level 94.65% compared with the regime of sulfuric-acid leaching developed previously. At the same time, consumption of sulfuric acid for leaching is reduced by 22%, the leaching period is six times shorter, and energy consumed for heating leaching pulp is lower by approximately a factor of three.

The purpose of the present study is to deal with the potential application of jarosite, a waste material produced during the extraction of zinc ore concentrate using the hydro metallurgy operation, in the production of the concrete. The method involves a total of five mixes including the control mix which was prepared by partially replacing the cement by the jarosite varying from 10, 15, 20 and 25%. It was noticed that incorporation of jarosite did not much alter the fresh concrete properties, as it was well within the desired range. The present laboratory investigation results also confirmed that as the percentage of jarosite in the concrete mix was increased, the mechanical properties of the concrete tend to decrease gradually but can be improved further by adding mineral and chemical admixtures. Further, the water absorption properties were also got improved. Other durability properties like acid attack, chlorine resistance and abrasion loss were found to decrease as the percentage of the jarosite in the concrete mix was increased. From the study, it can be concluded that, up to 15% of jarosite can be used as the replacement of the cement in the construction of the highways. Higher percentage of the jarosite can be used for low traffic volume or village roads for the safe disposal and reuse of the industrial waste.

The pre-treatment of zinc oxide bearing ores with high slime content is important to ensure that resources are utilized optimally. This paper reports an improved process using hydrocyclone de-sliming, dispersion reagents, and magnetic removal of iron minerals for the pre-treatment of zinc oxide ore with a high slime and iron content, and the benefits compared to traditional technologies are shown. In addition, this paper investigates the damage related to fine slime and iron during zinc oxide flotation, the necessity of using hydrocyclone de-sliming together with dispersion reagents to alleviate the influence of slime, and interactions among hydrocyclone de-sliming, reagent dispersion, and magnetic iron removal. Results show that under optimized operating conditions the entire beneficiation technology results in a flotation concentrate with a Zn grade of 34.66% and a recovery of 73.41%.

The object studied is Shaimerden oxidized zinc ore deposit containing zinc, lead, copper, iron, calcium, magnesium, aluminum, manganese and silicon. Chemical and mineralogical composition of the ore are investigated. It is established that ore coarse fraction contains more zinc carbonate and less zinc silicate compared with undersize particles. In addition, ore coarse fraction is richer in residual forms (nontronite, sphalerite) hardly soluble in sulphuric acid solution. Thermodynamic analysis of probable transformations during leaching is carried out, kinetics of coarse fraction and undersize particles of ore leaching is studied, and Pourbaix diagrams are plotted for analysis of processes occurring at a phase interface during leaching of oxidized zinc ore. Studies for stripping oxidized zinc ore are carried out on large (–20+1 mm) and small (–1+0 mm) fractions. Optimum leaching parameters are established for fine and coarse ore fractions: sulfuric acid concentration and process temperature and duration (C(H2SO4) = 150–160 g/liter, temperature 60°C, leaching time 60 min). Dependences are determined for the degree of zinc extraction into solution on sulphuric acid concentration, temperature, and leaching duration for coarse and fine ore factions.

Dating of lead-zinc deposits is of critical importance for better understanding of ore genesis, but has long been a big challenge due to the lack of suitable minerals that can be unequivocally linked to the ore genesis and that can be used for tradition radiometric methods. This kind of deposits have simple mineralogy dominated by galena and sphalerite commonly associated with calcite and other gangue minerals. Both galena and sphalerite have low and high variable Re concentrations and thus Re-Os dating of these minerals have been less promising. In addition, the recovery of Re is extremely low for galena when conventional method was applied, lending additional difficulty in precisely dating galena. In this study, we investigate the recovery of Re using different media for anion exchange separation and reporte a revised preparation method for Re-Os dating of galena and sphalerite. By using the new protocol, two reliable Re-Os isochron ages of galena and sphalerite from the Fule (20.4±3.2 Ma) and Laochang (308±25 Ma) Pb-Zn deposits in Yunnan Province, SW China, are achieved.

Polymetallic sulfide ores (Zn, Pb, Fe, Cu, Ag, and Cd) found in the Alanish locality of northern Iraq are hosted by dolostone in the Late Permian Chia Zairi Formation. The Alanish locality is one of several Zn–Pb deposits that are widespread in northern Iraq, situated along the northern passive margin of the Arabian plate. This paper describes the ore deposit classification, mineral chemistry, and paragenetic sequence of the area and proposes an ore formation model. We report the presence of acanthite and greenockite for the first time in Iraq. A brine solution derived from the sedimentary basin formed the primary sulfide ore minerals (sphalerite, galena, acanthite, pyrite, chalcopyrite, greenockite, and marcasite). The pre-tectonic mineralization is characterized by replacement textures including (1) high-Fe, low-Zn, dark-colored, coarse-grained sphalerite; (2) deformed anisotropic coarse-grained galena; and, (3) idiomorphic cubes of crushed pyrite. Conversely, the post-tectonic mineralization is characterized by open-space filling textures, including (1) low-Fe, high-Zn, light-colored, fine aggregated sphalerite; (2) fine-grained galena; and, (3) the existence of acanthite and marcasite. Although galena is an Ag carrier, both mineralization phases contained non-argentiferous galena. Non-sulfides (smithsonite, cerussite, and goethite) have replaced older sulfides in many areas due to supergene process. Gangue minerals present are dolomite, calcite, barite, and siderite. Open spaces and cavity filling of small paleo-karsts, replacement, veins, and veinlets are common features of the ore body. Metals were sourced from brines generated in the sedimentary basin, whereas sulfur was derived from nearby evaporates. Sediment compaction and tectonic activity, probably during Late Cretaceous, were the driving forces that squeezed and moved ore-bearing fluids derived from the sedimentary basin. Multiple stages of ore-bearing fluids were epigenetically intruded into the Late Paleozoic dolostone, forming an epigenetic strata-bound Mississippi Valley-type deposit precipitated under a temperature of 120 °C, as indicated by the cadmium fractionation in sphalerite and galena. Dolomitization and tectonic activity provided the necessary permeability for accumulating ores. The main ore body is directly connected to a fault plane and to adjacent dolostone that is frequently fractured and brecciated.

The catalytic-oxidative leaching of a mixed ore, which consists of low-grade oxide copper ore and oxide zinc ore containing ZnS, was investigated in ammonia-ammonium sulfate solution. The effect of the main parameters, such as mass ratio of copper ore to zinc ore, liquid-to-solid ratio, concentration of lixivant, leaching time, and temperature, was studied. The optimal leaching conditions with a maximum extraction of Cu 92.6 pct and Zn 85.5 pct were determined as follows: the mass ratio of copper ore to zinc ore 4/10 g/g, temperature 323.15 K (50 °C), leaching time 6 hours, stirring speed 500 r/min, liquid-to-solid ratio 3.6/1 cm3/g, concentration of lixivant including ammonia 2.0 mol/dm3, ammonium sulfate 1.0 mol/dm3, and ammonium persulfate 0.3 mol/dm3. It was found that ZnS in the oxide zinc ore could be extracted with Cu(II) ion, which was produced from copper ore and was used as the catalyst in the presence of ammonium persulfate.

Prior to the mastering of metallic zinc production in the mid-19th century, brass making in Europe was based on the so-called cementation process: within a more or less closed vessel, gaseous zinc is produced by the carbothermic reduction of zinc ore at around 1,000°C (±100°C), and simultaneously diffuses into metallic copper. Few ancient brass objects dated before the Industrial Revolution analyzed so far bear more than 30 wt.% zinc, so that this zinc content value has become a dating criterion for these artifacts. The systematic laboratory-scale experimental simulations of the ancient process presented here permit the multiple influences of temperature, isothermal treatment duration, and initial Zn/Cu ratio on the zinc content of the final products, and on the zinc recovery rates as well, to be investigated for the first time.

The Tres Marias carbonate-hosted Zn–Ge deposit in Chihuahua, Mexico contains sphalerite with the highest average Ge (960 ppm) and willemite with the highest reported Ge contents of Mississippi-Valley-type (MVT) deposits worldwide. This has prompted current exploration efforts to focus on the deposit as a high-grade source of germanium. The sulfide-rich ore type (>125,000 t at 20% Zn and 250 g/t Ge) contains Fe-rich botryoidal sphalerite (type I) associated with solid hydrocarbons. This type exhibits distinctive intimately intergrown lamellar texture of high-Fe sphalerite (average 9.9 wt.% Fe and 800 ppm Ge) and a somewhat less Fe-rich sphalerite phase (average 5.5 wt.% Fe and 470 ppm Ge). Reddish-brown banded sphalerite (type II, average 5.7 wt.% Fe and 1,320 ppm Ge) is subordinately followed by galena and pyrite. The sulfide-poor “oxidized” zinc ore (up to 50 wt.% Zn; 250 to 300 ppm Ge) is a fine-grained, often friable, alteration product of the sulfide ore and associated limestone and breccia host. While some areas are dominated by carbonates and sulfates, others are enriched in silicates such as hemimorphite and willemite. The gangue assemblage includes goethite, hematite, and amorphous silica or quartz. Minor wulfenite, greenockite, cinnabar, and descloizite also occur. Willemite occurs as interstitial replacement of sphalerite and fracture fillings in the oxidized ore and can be unusually rich in Pb (up to 2.0 wt.%) and Ge (up to 4,000 ppm). Oscillatory zonation reflects trace element incorporation into willemite from the oxidation of primary Ge-bearing sphalerite and galena by siliceous aqueous fluids. The Tres Marias deposit has hybrid characteristics consisting of a primary low-temperature MVT Ge-rich Zn–Pb sulfide ore body, overprinted by Ge-rich hemimorphite, willemite, and Fe oxide mineralization.

The leaching of zinc concentrate obtained from the zinc ore located in the Ganesh-Himal region of Nepal has been carried out in the presence of ammonium persulfate (APS) as an oxidant. Leaching variables such as time, temperature, acid, and oxidant concentration, E h , and particle size of sphalerite concentrate were studied to optimize the condition and to understand the mechanism of the reaction. The zinc extraction increased up to a temperature of 333 K and a further rise in the temperature to 343 K resulted in lowering of metal extraction. A decrease in particle size and increase in oxidant concentration enhanced the dissolution rate of zinc. The leaching data best fitted to the mixed controlled kinetic model. An activation energy of 43 kJ/mol was obtained for the dissolution of zinc in the temperature range 303 to 333 K with APS. The leaching mechanism was further established by characterizing the original concentrate and the leach residue by X-ray diffraction (XRD) phase identification and scanning electron microscopy (SEM) studies.

Polished ore samples from the world-class Bleiberg lead-zinc deposit in Austria were studied by Field Emission Scanning Electron Microscopy (FESEM) at magnifications in the range of 105–106. The zinc ore shows nano-sized sphalerite filaments and spherules which are morphologically similar to recent biofilms of sulphate-reducing bacteria. The activity of sulphate-reducing bacteria is suggested by a large δ34S ‰ difference of ~40‰ between coeval seawater sulphate (+16 ‰) and sulphide sulphur (< −25 ‰) in the Bleiberg ores, and by variable sulphur valences. Peloids of sphalerite, Zn-bearing calcite and pyrite have features typical of bacterial colonies. Combined with geological and mineralogical evidence, a significant role of bacteria during ore deposition at Bleiberg is likely.

A comparative study of the concentrations of cadmium in ecosystems developed on tailings from lead/zinc mines was undertaken. Mine soils, vegetation, ground-dwelling invertebrates and Apodemus sylvaticus from nine historic and abandoned mines in Wales and a modern Irish mine site were sampled in order to evaluate and compare exposure risks to wildlife. There were three high soil cadmium sites (155–300 mg kg-1) all from north-east Wales sites, one intermediate site (21 mg kg-1) the Irish mine tailings, with the other sites having low (background) cadmium levels. The cadmium levels reflected differencesin ore minerology and in particular the presence of the zinc ore, sphalerite. The highest plant and invertebrate cadmium levels generally occurred in the three high soil cadmium sites. However, occasional high levels were found in plant and invertebrate samples from one or more of the low cadmium sites. Of particular significance was, despite the relatively high soil cadmium, the very low cadmium concentrations in the plants and invertebrates from the Irish tailings. Evidence of food-chain transfer and even biomagnification in invertebrates did not lead to high cadmium levels in kidneys of A. sylvaticus. Onlyat one high site were the kidney cadmium residues significantly higher than the reference site.

Experimental studies on phase equilibria and liquidus in the multicomponent system PbO-ZnO-CaO-SiO2-FeO-Fe2O3 in air have been conducted over the temperature range between 1323 K (1050 °C) and 1623 K (1350 °C) to characterize the phase relations of the complex slag systems encountered in lead and zinc blast furnace sinters. The liquidus in two pseudoternary sections ZnO-“Fe2O3”-(PbO + CaO + SiO2) with the CaO/SiO2 weight ratio of 0.933 and PbO/(CaO + SiO2) weight ratios of 2.0 and 3.2 have been constructed.

Two types of laboratory cells have been constructed to electrowin zinc from sulfate electrolytes: one cell was cylindrical while the other had a rectangular (flat) geometry. Cells were operated on industrial or synthetic electrolytes to electrodeposit zinc onto a spouted bed of zinc particles in the range of 0.75 to 1.45 mm. Current efficiencies and cell voltages have been measured during the course of batch experiments, enabling the calculation of the energy consumption per kilogram of zinc deposited. Electrolyte samples have been analyzed. Current densities (current per unit of cell cross-sectional area) were in the range of 1380 to 6200 A/m2. Most catholytes were initially neutral and contained on the order of 150 g/L of zinc. Final acid contents were in the range of 39 to 114 g/L of sulfuric acid. The performance of the cells (particularly with respect to current efficiency) was superior to prior work on fluidized bed electrowinning from similar electrolytes. The flat cell was superior to the cylindrical cell and showed energy consumptions of less than 3 kWh/kg zinc at current densities up to 3500 A/m2 when used to take the zinc content from 150 to 100 g/L zinc. Current efficiencies in this application ranged from 91 to 92 pct.

A mineralogical study was carried out on the neutral leach residue and weak acid leach residue generated from Gordonsville zinc concentrate at the Clarksville Electrolytic Zinc Plant of Savage Zinc Inc. The intent was to characterize the mineral forms and associations of germanium. The Gordonsville zinc concentrate consists mostly of sphalerite which has a solid solution Ge content of ~400 ppm; the sphalerite is the dominant, if not only, Ge carrier in the concentrate. The neutral leach residue consists principally of iron gel-silica gel, ZnO, and basic zinc sulfate, (Zn,Cu)4(SO4)(OH)6·4H2O, together with minor amounts of ZnFe2O4, sphalerite, Zn2SiO4, Zn-Fe-Pb silicate, and PbSO4, as well as traces of quartz, silicates, Pb-K jarosite solid solution, Fe2O3, and FeO·OH. The major Ge carrier is the iron gel-silica gel phase, but modest amounts of Ge are present in the ZnO, ZnFe2O4, sphalerite, and Zn-Fe-Pb silicate phases. The weak acid leach residue consists mostly of iron gel-silica gel, ZnFe2O4, PbSO4, Pb-K jarosite, Zn-Fe-Pb silicate, and quartz. The major Ge carrier is the iron gel-silica gel phase which contains up to 1.7 pct Ge and accounts for ~70 pct of the total Ge content of this residue. The remaining Ge is carried by the Zn-Fe-Pb silicate, ZnFe2O4, and some of the rare Mn-Pb-Fe oxide phases.

Liquid sulfur-zinc sulfate solution interfacial tensions and liquid sulfur-zinc sulfate solution-zinc sulfide (marmatite) contact angles were measured in the absence and presence of surface-active agents. Interfacial tensions measured varied between 54 ± 1 mN/m in the surfactant-free system and 20 ± 1 mN/m in the presence of a surfactant. The liquid sulfur-zinc sulfide mineral-zinc sulfate solution contact angle varies between 80 ± 5 deg, in the absence of any surfactant, and 148 ± 5 deg, depending on the surfactant used. The surface-active agents were used as dispersants for sulfur in bench-scale zinc pressure-leaching experiments. The observed extent of zinc extraction depends on the surfactant and varies from 40 to 96 pct.

An indirect complexometric method is described for the determination of zinc(II) using 2,2′-bipyridyl as masking agent. Zinc(II) in a given sample solution is initially complexed with an excess of EDTA and surplus EDTA is titrated with lead nitrate solution at pH 5.0–6.0 (hexamine), using xylenol orange as indicator. An excess of 2,2′-bipyridyl is then added, the mixture shaken well and the EDTA released from the Zn-EDTA complex is titrated with standard lead nitrate solution. Results are obtained for 3–39 mg of Zn with relative errors ≤ 0.5% and standard deviations ± 0.06 mg. The interference of various ions are studied. The method is applied for the determination of zinc in its alloys and ores.

A new concept has been developed for the production of zinc from zinc and complex zinc concentrates. It is a two-stage process involving oxidation of zinc sulfide to oxide and dissolution into slag and the fuming of zinc from the slag by injecting carbonaceous materials into it to produce zinc vapors which can be subsequently condensed in a lead-splash condenser such as those used in the Imperial Smelting Process (ISP). In this paper, the effects of the quantity of air, temperature, and concentrate feed rate have been discussed on the production of zinc-rich slag, which is the first stage of the proposed process.

The possibility of production of ceramic floor tile based on kaolin from the Angrenskoe Deposit and flotation waste from a lead-zinc plant (SOF) is studied. The main physicochemical properties of ceramic specimens sintered from mixtures with different contents of kaolin and SOF are described. An optimum temperature regime for the firing process is suggested.

Oxygen isotope fractionation in the zinc oxides has been calculated by means of the modified increment method. The results suggest that zincite is slightly enriched in 18O relative to the franklinite of the spinel-type structure but considerably depleted in 18O relative to the franklinite of the inverse spinel-type structure. The zinc oxides are significantly depleted in 18O relative to water under hydrothermal and metamorphic conditions. The oxygen isotope analyses of mineral pairs including the zinc oxides and the common gangue minerals such as calcite and quartz can constitute a sensitive isotope geothermometer. Application of oxygen isotope geothermometry to natural assemblages is attempted for the calcite-zinc ore mineral pairs from the Sterling Hill deposit in USA. The results indicate that the temperature of the zinc mineralization may be in the range from 410° to 630 °C and thus lower than the metamorphic temperatures of granulite facies. A metamorphic fluid could have been involved in the formation of the zinc ore minerals. Franklinite would structurally be an inverse spinel in the infancy of its formation, and thus could have originally evolved from Zn2 + substitution to Fe2 + of magnetite at the high temperatures.

A method has been developed for routine determination of fluorine in zinc sulfide ores by activation with fast neutrons from a 6.6 Ci227Ac−Be isotope source and counting of the 4.5 to 7 MeV gamma-rays of the product nuclide16N. Samples and standards consist of pellets pressed from a mixture of powdered material with wax or graphite. Samples and standards alternate in a sequence of 20 seconds irradiation, 4 seconds decay and 20 seconds counting. This analysis sequence, including the computation of the analysis results from the counting data automated by means of a LSI-11 Microprocessor with 12K×16 bit memory. The zinc ores, containing 0.3 to 0.7% fluorine have been analysed with a precision ranging from 1.56 to 1.33% relative. As a test for the reliability of the method, three standard reference materials were analysed in the same way as the zinc ore samples.

Energy dispersive X-ray fluorescence method for the determination of iron /3.5–26% of Fe/, zinc /0.5–9% of Zn/ and lead /0.05–5% of Pb/in zinc-lead ores containing arsenic has been worked out. In order to eliminate the interelement effect intensity correction equation had been proposed. The relative standard deviation of the determination varies from 3.6 to 9.2% depending on the element.

Computerized bibliographic databases have become sufficiently well developed and widely available to researchers that they have become potentially an important source of time series estimates of the growth of scientific literature. This paper uses the GEOREF3 database in such an application to estimation of the growth of geoscience. It is found by comparison with studies previously done from the hardcopy equivalents of GEOREF3 that the computer-derived time series can achieve results similar to their equivalents and do this more efficiently, more inexpensively and more comprehensively. Examples are given for geoscience as a whole, and for the literature related to several mineral commodities: iron ore, lead ore, nickel ore, petroleum and natural gas, radioactive minerals and ores, and zinc ore.

Laboratory studies have been conducted on the leaching of chalcopyrite and sphalerite with hypochlorous acid. The effects of stirring speed, temperature, pH, and hypochlorous acid concentration on the leaching rates have been determined. In addition, the leaching mechanisms have been resolved by analyzing the concentrations of the reaction products. It has been found that more than 90 pct extraction of both chalcopyrite and sphalerite can be achieved in one hour using less than 0.3 molar hypochlorous acid at room temperature. The primary leach products of chalcopyrite and sphalerite were sulfur and sulfate in the mole ratios of 1 to 1 and 2 to 1, respectively. A mixed kinetic model was applied to explain the leaching rates of chalcopyrite while a diffusion model was applied to explain the leaching rates of sphalerite. The mixed kinetic model involved steady-state diffusion of hypochlorous acid through the sulfur layer by a chemical reaction at the reaction interface. Good agreement between these models and the leaching rates of both minerals was obtained.

The dissolution of sphalerite in acidic ferric chloride solution was investigated in the temperature range 320 to 360 K. Both sized particles from three sources and polished flat surfaces were used as samples. The effect of stirring rate, temperature, ferric and ferrous ion concentration, purity, and particle size on the dissolution rate were determined. During the initial stages of the process chemical reaction at the mineral surface is rate controlling while during the later stages diffusion through the product sulfur layer is rate controlling. Overall the process follows the mixed-control model embodying both chemical reaction and diffusion. The activation energy for the dissolution of sphalerite particles was found to be 46.9 kJ/mol.

The Blazna-Guset mining area is located in the Rodna Mountains, Eastern Carpathians, North Romania. It is mostly covered by the metamorphic rocks of the Rebra Series (Upper Precambrian; K/Ar dating gave 800 m.y.). The middle part of this series — called the Carbonate Formation — contains lead-zinc pyrite ores hosted by prevailingly carbonate rocks. The ores form flat and thin lenses occurring together with fine intercalations of silicate-, graphite- and quartz-bearing rocks within the calcite-dominated limestones. Pyrite, ironpoor sphalerite and galena are the main ore minerals. Chalcopyrite, pyrrhotite and magnetite also occur in small amounts. Within the highly deformed and partly recrystallized parts of the ore bodies bournonite, arsenopyrite and pearceitepolybasite were locally encountered. Ba, Ti and Mn are the most significant ore-accompanying elements.

The formation of zinc ferrite (ZnFe2O4) during the fluidized-bed roasting of zinc concentrates presents subsequent processing difficulties both for zinc recovery and for iron separation and disposal. A major source of iron in these concentrates is from the iron sulfides — pyrite and pyrrhotite. This study examined the changes undergone by these iron minerals when roasted together with sphalerite at 1223 K in a fluidizing gas mixture of 3 pct oxygen and 97 pct nitrogen. Optical microscopy and electron microprobe analysis were employed to identify the three stages that lead to ferrite formation and to examine the processes that occur within each stage. The first stage is oxidation of the sulfides to highly vesicular, amorphous magnetite particles containing small amounts of zinc. The second stage involves both densification of these particles by sintering and counterdiffusion of iron and zinc cations to form a continuous phase of homogeneous zinc-rich spinel and a precipitate of hematite. In the third stage, continuation of cation diffusion and increasingPo 2 results in the formation of stoichiometric zinc ferrite. These observations have been interpreted by reference to the established phase relationships that occur in the Zn-Fe-O system, and a detailed, solid state reaction mechanism for the formation of zinc ferrite has been proposed.

Most of the production of germanium in the U. S. is from byproducts of smelting Tri-State zinc ore. Only in England has commercial manufacture of germanium been reported as a byproduct of the burning of coal.

For the AAS-determination of Se in zinc ore with high concentrations of lead and copper, the sample is dissolved in a nitric-hydrochloric acid mixture. Excess nitric acid is removed by heating with perchloric acid and hydrochloric acid is added to reduce Se(VI) to Se(IV). Thiourea is added to the sample aliquotes taken for hydride generation to minimize the interference from copper. The result for selenium agreed well with that found by NAA. Total standard deviation of the method is 5–10 %.

Ore Deposits By Prof. Charles F. Park jun., and Prof. Roy A. MacDiarmid. (A Series of Books in Geology.) Pp. x + 475. (San Francisco and London: W. H. Freeman and Company, 1964.) 70s.